β2 adrenergic receptor agonists are advantageously administered directly into the respiratory tract by inhalation when used for treating pulmonary or respiratory disorders. Several types of pharmaceutical inhalation devices have been developed for administering therapeutic agents by inhalation including dry powder inhalers (DPI), metered-dose inhalers (MDI) and nebuliser inhalers.
Liquid formulations, in particular aqueous formulations, are easy to administer since they are inhaled during normal breathing through a mouth-piece or a face-mask. They are particularly suitable for young and elderly people who are most often the patients in need of such therapy and who experience difficulties using other devices.
5-(2-{[6-(2,2-difluoro-2-phenylethoxy)hexyl]amino}-1-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one is claimed and described in published patent application WO 2006/122788 A1.
Although 5-(2-{[6-(2,2-difluoro-2-phenylethoxy)hexyl]amino}-1-hydroxyethyl)-8-hydroxyquinolin-2(1H)-one has shown adequate pharmacological behaviour it has proved difficult to obtain it in the form of a salt which is water-soluble and especially very stable when in aqueous solutions.
So far no water-soluble salt of 5-(2-{([6-(2,2-difluoro-2-phenylethoxy)hexyl]amino}-1-hydroxy-ethyl)-8-hydroxyquinolin-2(1H)-one having the desired properties has been reported.
Accordingly, a need exists for a water-soluble and stable salt of this compound which can be used in the preparation of aqueous solutions, particularly suitable for certain patient such us children and the elderly patients.